GENEVA, Switzerland - Incidents of modern-day slavery are only likely to increase as a result of some of the biggest challenges facing the world today, a UN expert outlined in a report for the Human Rights Council in Geneva on Monday.

The Special Rapporteur on contemporary forms of slavery, Urmila Bhoola, says over 40 million people are currently enslaved around the world, a quarter of them children.

Due to problems of environmental degradation, migration and shifting demographics, the scourge of modern-day slavery is expected to grow.

Over 60 percent of those in forced labour work in the private sector, Ms. Bhoola said, with women and girls disproportionately affected. Of the female victims involved in forced labour, an astonishing 98 percent have experienced sexual violence.

Global estimates from the International Labour Organization (ILO) indicate that 24.9 million people are in forced labour situations worldwide, and 15.4 million live in forced marriages.

This sort of trend, "must serve as a wakeup call," Ms. Bhoola said, highlighting that the astounding statistics come four years after countries set goals aimed at stamping out trafficking, ending violence against women, and eradicating modern slavery.

"In wake of climate change, people may lose their livelihoods, young people who don't have access to decent work may migrate through unsafe channels and changes in the world of work, such as automation, may push already vulnerable people out of their jobs," all of which could increase people's vulnerability to slavery, the expert explained.

Even for those who escape, life for survivors is often difficult. Investigations by Human Rights Watch, highlight how even victims who manage to extricate themselves, can return home to the same desperate circumstances that made them vulnerable to begin with, but now facing stigma or blame.

Beyond these tragic realities for individuals, "slavery leads to increased public health costs, productivity losses, negative environmental externalities and lost income," Bhoola added, urging countries and business to "act now."

"We cannot afford to stand by while more and people are driven into forced labour, servile marriage or child labour," she said.

Looking forward, the UN expert highlighted that for youth approaching working age, the situation is more dire - "By 2030, some 85 percent of the more than 25 million young people entering the labour force globally will be in developing and emerging countries," she noted. "Their perspectives to access jobs offering decent work will determine their level of vulnerability to exploitation, including slavery."

To prepare for this, "it is imperative" anti-slavery efforts are "systematic, scientific, strategic, sustainable, survivor-informed, and smart" she maintained.

Current efforts to end slavery are falling short and States and businesses "must take more decisive action to end slavery," Ms. Bhoola concluded. This must be done "by committing more resources to this effort and by adopting and implementing public policies which address contemporary forms of slavery effectively."